Technical Field
The disclosure relates generally to a photolithography process for manufacturing semiconductor devices, and specifically to a photomask capable of adjusting focal planes among different regions of the semiconductor devices, and a method of manufacturing the semiconductor devices using the photomask.
Related Art
In conventional semiconductor manufacturing methods, photomasks are used during photolithography in order to expose a semiconductor wafer to a pattern of intense light. This exposure causes a pattern to be formed on the semiconductor wafer, which alone or in combination with additional exposures (using the same or different photomask), can form the basis of the integrated circuit to formed on the semiconductor wafer. After the exposure, etching and/or deposition can be performed in order to form the circuit elements in the semiconductor wafer.
Conventional photomasks included a transparent baseplate having opaque elements corresponding to areas that are not to be exposed. The advent of smaller semiconductor features have necessitated the use of phase-shifting photomasks. Such phase-shifting photomasks are specifically designed only to allow for passing light to exit the photomask with either a zero degree phase shift (in exposure areas) or a 180 degree phase shift (in non-exposure areas).